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1.
Carbohydr Polym ; 340: 122293, 2024 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-38858005

RESUMEN

A few protein- and polysaccharide-based particles have shown promising potential as stabilizers in multi-phase food systems. By incorporating polymer-based particles and modifying the wettability of colloidal systems, it is possible to create particle-stabilized emulsions with excellent stability. A Pickering emulsifier (AGMs) with better emulsifying properties was obtained by the Maillard reaction between acid-hydrolysed agar and gelatin. Laser confocal microscopy imaging revealed that AGMs particles can be used as solid emulsifiers to produce a typical O/W Pickering emulsion, with AGMs adsorbing onto the droplet surface to form a dense interfacial layer. Cryo-scanning electron microscopy analysis showed that AGMs self-assembled into a three-dimensional network structure, which prevented droplets aggregation through strong spatial site resistance, contributing to emulsion stabilization. These emulsions exhibited stability within a pH range of 1 to 11, NaCl concentrations not exceeding 300 mM, and at temperatures below 80 °C. The most stable emulsion oil-water ratio was 6:4 at a particle concentration of 0.75 % (w/v). AGMs-stabilized Pickering emulsion was utilized to create a semi-solid mayonnaise as a replacement for hydrogenated oil. Rheological analysis demonstrated that low-fat mayonnaise stabilized with AGMs exhibited similar rheological behavior to traditional mayonnaise, offering new avenues for the application of Pickering emulsions in the food industry.


Asunto(s)
Agar , Emulsionantes , Emulsiones , Gelatina , Reacción de Maillard , Gelatina/química , Agar/química , Emulsiones/química , Emulsionantes/química , Reología , Concentración de Iones de Hidrógeno , Tamaño de la Partícula , Temperatura
2.
Int J Biol Macromol ; 268(Pt 1): 131451, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38614177

RESUMEN

In this study, citric acid successfully reacted with agar through the dry heat method, and citrate agar (CA) gel was used to stabilize O/W emulsions. The mechanisms of the CA structure and emulsion pH that affected emulsion stabilization were analyzed, and the application of CA gel emulsion (CAGE) was explored. Compared with native agar (NA), CA showed lower gel strength, higher transparency, and higher water contact angle. These changes indicate that a cross-linking reaction occurred, and it was demonstrated via FTIR and NMR. The emulsion properties were evaluated using particle size, ζ-potential, and the emulsification activity index. Results showed that CAGEs had a smaller particle size and lower ζ-potential than the native agar gel emulsion (NAGE). Meanwhile, confocal laser scanning microscopy confirmed that the CA gels stabilized the emulsions by forming a protective film around the oil droplets. Stability experiments revealed that CAGE (prepared with CA gel [DS = 0.145]) exhibited better stability than NAGE in the pH range of 3-11, and the rheological results further confirmed that the stability of the emulsions was influenced by the network structure and oil droplet interaction forces. Afterward, the application prospect of CAGE was evaluated by encapsulating vitamin D3 and curcumin.


Asunto(s)
Agar , Ácido Cítrico , Emulsiones , Tamaño de la Partícula , Emulsiones/química , Agar/química , Ácido Cítrico/química , Concentración de Iones de Hidrógeno , Geles/química , Reología , Agua/química , Colecalciferol/química
3.
Enzyme Microb Technol ; 175: 110410, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38340378

RESUMEN

Prunin of desirable bioactivity and bioavailability can be transformed from plant-derived naringin by the key enzyme α-L-rhamnosidase. However, the production was limited by unsatisfactory properties of α-L-rhamnosidase such as thermostability and organic solvent tolerance. In this study, biochemical characteristics, and hydrolysis capacity of a novel α-L-rhamnosidase from Spirochaeta thermophila (St-Rha) were investigated, which was the first characterized α-L-rhamnosidase for Spirochaeta genus. St-Rha showed a higher substrate specificity towards naringin and exhibited excellent thermostability and methanol tolerance. The Km of St-Rha in the methanol cosolvent system was decreased 7.2-fold comparing that in the aqueous phase system, while kcat/Km value of St-Rha was enhanced 9.3-fold. Meanwhile, a preliminary conformational study was implemented through comparative molecular dynamics simulation analysis to explore the mechanism underlying the methanol tolerance of St-Rha for the first time. Furthermore, the catalytic ability of St-Rha for prunin preparation in the 20% methanol cosolvent system was explored, and 200 g/L naringin was transformed into 125.5 g/L prunin for 24 h reaction with a corresponding space-time yield of 5.2 g/L/h. These results indicated that St-Rha was a novel α-L-rhamnosidase suitable for hydrolyzing naringin in the methanol cosolvent system and provided a better alternative for improving the efficient production yield of prunin.


Asunto(s)
Florizina/análogos & derivados , Spirochaeta , Metanol , Glicósido Hidrolasas/química , Solventes
4.
Int J Biol Macromol ; 263(Pt 2): 130051, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38350580

RESUMEN

A new type of core-shell microsphere was prepared by a pre-crosslinking method, consisting of cross-linked agarose microspheres as the core and agarose-dextran as the shell. After optimizing the preparation process, the microspheres with a uniform particle size were obtained and characterized using cryo-scanning electron microscopy to determine their surface and cross-sectional morphology. Results from flow rate-pressure and chromatographic performance tests showed that the core-shell agarose microspheres were supported by the core microspheres and composed of composite polysaccharides, forming an interpenetrating polymer network structure as a hard shell. The core-shell agarose microspheres showed a 300.5 % increase in linear flow rate compared to composite polysaccharide microspheres prepared from shell materials and a 141.5 % increase compared to 6 % agarose microspheres. Additionally, the large pore structure of the shell combined with the fine pore structure of the core improved the material separation efficiency in the range of 0.1-2000 kDa. These findings suggest that core-shell natural polysaccharide microspheres have great potential as a separation chromatographic medium.


Asunto(s)
Dextranos , Microesferas , Sefarosa , Estudios Transversales , Microscopía Electrónica de Rastreo
5.
Int J Biol Macromol ; 255: 128196, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-37984583

RESUMEN

Antioxidant and antimicrobial agarose coatings were developed by grafting gallic acid through the carbodiimide coupling method. Structural characterization revealed that the carboxyl group of gallic acid was successfully grafted onto the C6-OH of D-galactose in agarose, with the highest observed grafting ratio being 13.73 %. The grafting of gallic acid significantly increased the antioxidant and bacteriostatic activities of the agarose. As the grafting ratio of gallic acid-modified agarose (GaAg) increased from 0 to 13.73 %, the scavenging ratio of DPPH and the inhibition ratio of ß-carotene bleaching were observed to increase from 0 % to 65.92 % and 6.89 % to 73.46 %, respectively. GaAg exhibited up to 100 % inhibition of Escherichia coli and Staphylococcus aureus. The physicochemical properties of gel strength, viscosity, gelling temperature and melting temperature decreased to 971.3 g/cm2, 17.9 mPa·s, 31.7 °C and 84.1 °C, respectively. The gel contact angle was increased from 22.1° to 73.6°. Fish preservation tests have demonstrated that it effectively inhibited bacterial growth, prevented fat oxidation, blocked light, reduced moisture loss, and enhanced the overall quality of grass carp (Ctenopharyngodon idellus) fillets during refrigeration, which was more effective than native agarose in extending the shelf life of fish. Therefore, GaAg holds promise as an aquatic product preservative.


Asunto(s)
Antioxidantes , Carpas , Animales , Antioxidantes/farmacología , Ácido Gálico , Sefarosa , Embalaje de Productos
6.
Int J Biol Macromol ; 253(Pt 5): 127185, 2023 Dec 31.
Artículo en Inglés | MEDLINE | ID: mdl-37797859

RESUMEN

Pickering emulsions was successfully fabricated using ball-milled agar particles with sizes and sulfate content around 7 µm and 0.62 %, respectively. These particles were obtained through a simple media-milling process using agar powders initially sized at 120 µm. The lamellated agar is aggregated into a mass after the milling process. The surface charge and hydrophobicity of the ball-milled agar particles were characterized through zeta potential and contact angle measurements, respectively. The droplet size of Pickering emulsions was related to oil fraction and particle concentration, ranging from approximately 45 µm to 80 µm. Ball-milled agar stabilized emulsions were sensitive to pH and salt conditions. The results of confocal laser scanning microscopy and cryo-SEM showed that at low particle concentrations and oil fractions, ball-milled agar stabilized the emulsions by dispersing particles on the surface of the oil droplets through electrostatic repulsion. Conversely, ball-milled agar stabilized the emulsions under high particle concentrations and oil fractions by forming a gel network structure to bind the oil droplets. In this research, this developed method provides the basis for the high-value application of agar and a new idea for preparing stable food-grade Pickering emulsion-based functional foods using raw-food material without surface wettability.


Asunto(s)
Emulsionantes , Emulsiones/química , Agar , Emulsionantes/química , Interacciones Hidrofóbicas e Hidrofílicas , Humectabilidad , Tamaño de la Partícula
7.
Mar Drugs ; 21(5)2023 May 14.
Artículo en Inglés | MEDLINE | ID: mdl-37233493

RESUMEN

Numerous compounds present in the ocean are contributing to the development of the biomedical field. Agarose, a polysaccharide derived from marine red algae, plays a vital role in biomedical applications because of its reversible temperature-sensitive gelling behavior, excellent mechanical properties, and high biological activity. Natural agarose hydrogel has a single structural composition that prevents it from adapting to complex biological environments. Therefore, agarose can be developed into different forms through physical, biological, and chemical modifications, enabling it to perform optimally in different environments. Agarose biomaterials are being increasingly used for isolation, purification, drug delivery, and tissue engineering, but most are still far from clinical approval. This review classifies and discusses the preparation, modification, and biomedical applications of agarose, focusing on its applications in isolation and purification, wound dressings, drug delivery, tissue engineering, and 3D printing. In addition, it attempts to address the opportunities and challenges associated with the future development of agarose-based biomaterials in the biomedical field. It should help to rationalize the selection of the most suitable functionalized agarose hydrogels for specific applications in the biomedical industry.


Asunto(s)
Materiales Biocompatibles , Hidrogeles , Sefarosa/química , Hidrogeles/química , Materiales Biocompatibles/química , Ingeniería de Tejidos , Sistemas de Liberación de Medicamentos
8.
Int J Biol Macromol ; 239: 124254, 2023 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-37003393

RESUMEN

Agar benzoate (AB) with different degrees of substitution (DS) was synthesized by the esterification of agar and benzoic anhydride in aqueous solution. The DS could be regulated by adjusting composition ratio, pH, and temperature. Its chemical structure was determined by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). 13C NMR spectrum of the AB suggested the main substitution occurred at the C-6 in the d-galactopyranose. Cryo-scanning electron microscopy (Cryo-SEM) showed that the aperture of AB was larger than that of agar. The thermal performance of AB decreased slightly, but this did not affect its performance. AB showed the highest relative antibacterial activity against Escherichia coli, S. aureus and Alternaria alternata, reaching 100 % (AB 20 g/L), 100 % (AB 40 g/L) and 19.35 % (7 d incubation), respectively. Moreover, the obtained AB possessed good emulsion stability. These antibacterial AB have broad application prospects in the field of fruit and vegetable preservation.


Asunto(s)
Antibacterianos , Staphylococcus aureus , Agar/química , Espectroscopía Infrarroja por Transformada de Fourier , Antibacterianos/farmacología , Antibacterianos/química , Benzoatos/farmacología
9.
Front Med (Lausanne) ; 10: 1079165, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-36844224

RESUMEN

Objectives: To evaluate COVID-19 vaccines in primary prevention against infections and lessen the severity of illness following the most recent outbreak of the SARS-CoV-2 Omicron variant in Shanghai. Data sources: Data from 153,544 COVID-19 patients admitted to the Shanghai "Four-Leaf Clover" Fangcang makeshift shelter hospital were collected using a structured electronic questionnaire, which was then merged with electronic medical records of the hospital. For healthy controls, data on vaccination status and other information were obtained from 228 community-based residents, using the same structured electronic questionnaire. Methods: To investigate whether inactivated vaccines were effective in protecting against SARS-CoV-2 virus, we estimated the odds ratio (OR) of the vaccination by comparing cases and matched community-based healthy controls. To evaluate the potential benefits of vaccination in lowering the risk of symptomatic infection (vs. asymptomatic), we estimated the relative risk (RR) of symptomatic infections among diagnosed patients. We also applied multivariate stepwise logistic regression analyses to measure the risk of disease severity (symptomatic vs. asymptomatic and moderate/severe vs. mild) in the COVID-19 patient cohort with vaccination status as an independent variable while controlling for potential confounding factors. Results: Of the 153,544 COVID-19 patients included in the analysis, the mean age was 41.59 years and 90,830 were males (59.2%). Of the study cohort, 118,124 patients had been vaccinated (76.9%) and 143,225 were asymptomatic patients (93.3%). Of the 10,319 symptomatic patients, 10,031 (97.2%), 281 (2.7%), and 7 (0.1%) experienced mild, moderate, and severe infections, respectively. Hypertension (8.7%) and diabetes (3.0%) accounted for the majority of comorbidities. There is no evidence that the vaccination helped protect from infections (OR = 0.82, p = 0.613). Vaccination, however, offered a small but significant protection against symptomatic infections (RR = 0.92, p < 0.001) and halved the risk of moderate/severe infections (OR = 0.48, 95% CI: 0.37-0.61). Older age (≥60 years) and malignant tumors were significantly associated with moderate/severe infections. Conclusion: Inactivated COVID-19 vaccines helped provide small but significant protection against symptomatic infections and halved the risk of moderate/severe illness among symptomatic patients. The vaccination was not effective in blocking the SARS-CoV-2 Omicron Variant community spread.

10.
Int J Biol Macromol ; 231: 123524, 2023 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-36736981

RESUMEN

Agar was modified with glutaric anhydride (GA) in this study to expand its application in food and medicine. Glutaric anhydride-modified agar (GAR) can maintain high gel strength (1247.4 g/cm2) and improved transparency (82.7 %). The esterified agar formed by GA further formed a cross-linking molecule structure by increasing the reaction temperature. Notably, excellent freeze-thaw stability (24.1 %) and swelling property (3116.6 %) of GAR indicated that the carboxyl-terminal of modified agar improves its affinity with water. Therefore, satisfactory water permeability and expansive stone enable agar films to achieve high water absorption. Furthermore, GAR films exhibit a specific absorption capacity of tetracycline hydrochloride in weak acid solution, thereby suggesting its potential application as a sustainable drug delivery carrier. Finally, the structure of the modified agar was analyzed to explain the mechanism of binding water. Cryo-scanning electron microscopy (SEM) depicted the porous structure of the agar gel responsible for swelling, drug loading, and release. Low-field NMR results showed that GA improves agar gel's binding and free water content. According to our research results, these GAR hydrogel membranes with excellent properties have the potential to be used as effective drug delivery materials.


Asunto(s)
Materiales Biocompatibles , Portadores de Fármacos , Agar/química , Fenómenos Químicos , Portadores de Fármacos/química , Agua/química
11.
Carbohydr Polym ; 308: 120644, 2023 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-36813337

RESUMEN

In this study, three kinds of anhydrides with different structures were introduced into agar molecules to study the effects of varying degrees of substitution (DS) and anhydride structures on the physicochemical properties and curcumin (CUR) loading capacity. Increasing the carbon chain length and saturation of the anhydride affects the hydrophobic interaction and hydrogen bonding of the esterified agar, thereby changing the stable structure of the agar. Although the gel performance declined, the hydrophilic carboxyl group and the loose porous structure provide more binding sites for the adsorption of water molecules, hence providing excellent water retention (1700 %). Next, CUR was used as a hydrophobic active ingredient to study agar microspheres' drug encapsulation and in vitro release ability. Results showed that the excellent swelling and hydrophobic structure of esterified agar could promote the encapsulation of CUR (70.3 %). The release process is controlled by pH, and the release of CUR under weak alkaline conditions is significant, which can be explained by the pore structure, swelling characteristics, and carboxyl binding of agar. Therefore, this study shows the application potential of hydrogel microspheres in loading hydrophobic active ingredients and sustained release and provides the possibility for the application of agar in drug delivery systems.


Asunto(s)
Curcumina , Curcumina/química , Agar , Portadores de Fármacos/química , Sistemas de Liberación de Medicamentos , Interacciones Hidrofóbicas e Hidrofílicas
12.
Nutr Metab (Lond) ; 19(1): 84, 2022 Dec 28.
Artículo en Inglés | MEDLINE | ID: mdl-36578045

RESUMEN

BACKGROUND: Evidence from previous studies has suggested that ginger extract exhibits the potential as an alternative treatment for Coronavirus disease 2019 (COVID-19). Here, we want to investigate whether ginger supplement improves the clinical manifestation of hospitalized COVID-19 individuals. METHODS: A total of 227 hospitalized individuals with COVID-19 were randomized to either the control (n = 132) or intervention group (n = 95). The intervention group took ginger supplement orally at the dosage of 1.5 g twice daily, until they were discharged from the hospital. Both groups received the same standard of general medical care during hospitalization, and the length of stay was recorded and compared between groups. RESULTS: Among all participants, a significant reduction in hospitalization time (the difference between the treatment and control groups was 2.4 d, 95% CI 1.6-3.2) was detected in response to the ginger supplement. This effect was more pronounced in men, participants aged 60 years or older, and participants with pre-existing medical conditions, relative to their counterparts (P-interactions < 0.05 for all). CONCLUSION: Ginger supplement significantly shortened the length of stay of hospitalized individuals with COVID-19. TRIAL REGISTRATION: The trial was registered on the Chinese Clinical Trial Registry (ChiCTR2200059824).

13.
Mar Drugs ; 20(12)2022 Dec 16.
Artículo en Inglés | MEDLINE | ID: mdl-36547930

RESUMEN

κ-carrageenases are members of the glycoside hydrolase family 16 (GH16) that hydrolyze sulfated galactans in red algae, known as κ-carrageenans. In this study, a novel κ-carrageenase gene from the marine bacterium Rhodopirellula sallentina SM41 (RsCgk) was discovered via the genome mining approach. There are currently no reports on κ-carrageenase from the Rhodopirellula genus, and RsCgk shares a low identity (less than 65%) with κ- carrageenase from other genera. The RsCgk was heterologously overexpressed in Escherichia coli BL21 and characterized for its enzymatic properties. RsCgk exhibited maximum activity at pH 7.0 and 40 °C, and 50% of its initial activity was retained after incubating at 30 °C for 2 h. More than 70% of its activity was maintained after incubation at pH 6.0-8.0 and 4 °C for 24 h. As a marine derived enzyme, RsCgk showed excellent salt tolerance, retaining full activity in 1.2 M NaCl, and the addition of NaCl greatly enhanced its thermal stability. Mass spectrometry analysis of the RsCgk hydrolysis products revealed that the enzyme had high degradation specificity and mainly produced κ-carrageenan disaccharide. Comparative molecular dynamics simulations revealed that the conformational changes of tunnel-forming loops under salt environments may cause the deactivation or stabilization of RsCgk. Our results demonstrated that RsCgk could be utilized as a potential tool enzyme for efficient production of κ-carrageenan oligosaccharides under high salt conditions.


Asunto(s)
Tolerancia a la Sal , Cloruro de Sodio , Carragenina/química , Bacterias/metabolismo , Glicósido Hidrolasas/metabolismo , Proteínas Bacterianas/metabolismo
14.
Carbohydr Polym ; 297: 120035, 2022 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-36184179

RESUMEN

A novel agar-based Pickering emulsion stabilizer was developed through the hydrophobic modification and microgelation of agar. After hexanoylation, the three-phase contact angle of hexanoylated agar (HAG) particles was adjusted from approximately 60° to 96° closing to neutral wettability. After microgelation, the particle size of the modified agar microgel was approximately 2 µm and Zeta potential reached -23.63 mV. Confocal laser microscopy and cryogenic scanning electron microscopy showed that HAG microgels formed a gel network or embedded on the surface of oil droplets, thus providing a dense barrier for oil droplets to coalesce and Ostwald ripening. The oil volume fraction and particle concentration had a significant effect on the droplet size and rheological properties of the Pickering emulsion. Pickering emulsion gels with long-term storage stability was prepared at low particle concentrations (0.7 wt%) and lower oil fractions (φ = 0.3- 0.5), which might become a new effective delivery system for bioactive substances.


Asunto(s)
Microgeles , Agar , Emulsiones/química , Geles/química , Interacciones Hidrofóbicas e Hidrofílicas , Tamaño de la Partícula
15.
Int J Biol Macromol ; 222(Pt A): 41-54, 2022 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-36156340

RESUMEN

In this study, a new method for preparing macroporous rigid agarose microspheres was developed by one-step pre-crosslinking method with cyclic anhydride. Three different cyclic anhydrides, namely, maleic anhydride, succinic anhydride, and glutaric anhydride, were used to pre-crosslink agarose. The reaction temperature and the amount of cyclic anhydride in the pre-crosslinking process were optimized to endow agarose with stronger cross-linking. Under the optimal cross-linking condition, macroporous rigid agarose microspheres with homogeneous particle size were successfully obtained by adjusting emulsification method. Cryo-scanning electron microscopy was used to characterize the morphology of cross-linked agarose gel and microspheres. The addition of cyclic anhydride increased the gel aperture of cross-linked agarose microspheres, thereby making the macropores in the microspheres more dense and enhancing the mass transfer in the particles. Under low pressure, the cross-linked agarose microsphere column can effectively separate model proteins at linear flow rates three times higher than the agarose microsphere column. These results indicate that the developed agarose microspheres are a promising high-speed chromatographic medium.


Asunto(s)
Anhídridos , Anhídridos Maleicos , Microesferas , Sefarosa/química , Anhídridos/química , Tamaño de la Partícula
16.
Mar Drugs ; 20(7)2022 Jun 27.
Artículo en Inglés | MEDLINE | ID: mdl-35877712

RESUMEN

An eco-friendly method for ι-carrageenan extraction from seaweed Eucheuma denticulatum through boiling and using a low concentration of Ca(OH)2 is reported. Compared to the traditional method of ι-carrageenan extraction using NaOH, the reported method using Ca(OH)2 had the advantages of using 93.3% less alkali and 86.8% less water, having a 25.0% shorter total extraction time, a 17.6% higher yield, and a 43.3% higher gel strength of the product. In addition, we evaluated the gel properties and structures of ι-carrageenan products extracted by Ca(OH)2 (Ca-IC) and NaOH (Na-IC). The Fourier transform infrared spectroscopy results showed that the structures of Ca-IC and Na-IC did not change remarkably. The results of the thermogravimetric analysis and differential scanning calorimetry showed that Ca-IC had the same thermal stability as Na-IC. The results of the textural analysis showed that Ca-IC had a higher hardness and better chewiness compared to Na-IC. Rheological results indicated that Ca-IC and Na-IC exhibited shear-thinning and non-Newtonian fluid properties, whereas the viscosity of Ca-IC was less than that of Na-IC. In conclusion, this new method of ι-carrageenan extraction using Ca-IC is markedly better and yields higher quality carrageenan than the conventional method of using Na-IC.


Asunto(s)
Rhodophyta , Algas Marinas , Carragenina/química , Rhodophyta/química , Hidróxido de Sodio , Viscosidad
17.
Mar Drugs ; 20(2)2022 Feb 06.
Artículo en Inglés | MEDLINE | ID: mdl-35200655

RESUMEN

As an important enzyme involved in the marine carbon cycle, alginate lyase has received extensive attention because of its excellent degradation ability on brown algae, which is widely utilized for alginate oligosaccharide preparation or bioethanol production. In comparison with endo-type alginate lyases (PL-5, PL-7, and PL-18 families), limited studies have focused on PL-17 family alginate lyases, especially for those with special characteristics. In this study, a novel PL-17 family alginate lyase, Aly23, was identified and cloned from the marine bacterium Pseudoalteromonas carrageenovora ASY5. Aly23 exhibited maximum activity at 35 °C and retained 48.93% of its highest activity at 4 °C, representing an excellent cold-adaptation property. Comparative molecular dynamics analysis was implemented to explore the structural basis for the cold-adaptation property of Aly23. Aly23 had a high substrate preference for poly ß-D-mannuronate and exhibited both endolytic and exolytic activities; its hydrolysis reaction mainly produced monosaccharides, disaccharides, and trisaccharides. Furthermore, the enzymatic hydrolyzed oligosaccharides displayed good antioxidant activities to reduce ferric and scavenge radicals, such as hydroxyl, ABTS+, and DPPH. Our work demonstrated that Aly23 is a promising cold-adapted biocatalyst for the preparation of natural antioxidants from brown algae.


Asunto(s)
Antioxidantes/farmacología , Oligosacáridos/farmacología , Polisacárido Liasas/metabolismo , Pseudoalteromonas/metabolismo , Antioxidantes/metabolismo , Disacáridos/metabolismo , Depuradores de Radicales Libres/metabolismo , Depuradores de Radicales Libres/farmacología , Hidrólisis , Simulación de Dinámica Molecular , Monosacáridos/metabolismo , Oligosacáridos/metabolismo , Polisacárido Liasas/aislamiento & purificación , Temperatura , Trisacáridos/metabolismo
18.
Food Chem ; 381: 132164, 2022 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-35101707

RESUMEN

Chemical modification is often used to improve the gel properties of agar but inevitably weakens gel strength in practical applications. This study achieved a breakthrough in improving the gel properties of agar without reducing its gel strength through modification with succinic anhydride. Fourier transform infrared spectroscopy and carbon nuclear magnetic resonance analyses showed that succinic anhydride could be mono-succinylated, cross-linked, and desulfurized with agar. The transition from mono-succinylation to cross-linking of agar was achieved by attemperation. Interestingly, the gel transparency of mono-succinylated agar increased from 55% to 89%, but its gel strength remarkably decreased from 1073 g/cm2 to 188 g/cm2. Cross-linking endowed agar with a higher gel strength (815 g/cm2) and gel transparency (85.3%). Agar succinylation demonstrated more beneficial effects and further enhanced the water-retention capacity of agar powder (18.1 g/g), the swelling ratio of agar film (1736.2%), and the freeze-thaw stability of agar gel (30.3%, 7th).


Asunto(s)
Anhídridos Succínicos , Agar/química , Espectroscopía Infrarroja por Transformada de Fourier , Anhídridos Succínicos/química
19.
Int J Biol Macromol ; 201: 364-377, 2022 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-34998880

RESUMEN

Agar is modified by chemical methods to improve its functional properties and meet the increasing demand of the market. Some of the functional properties of agar are improved after chemical modification, while other properties are reduced, especially gel strength. This study aimed to comprehensively improve the functional properties of agar through acylation and crosslinking by reacting with maleic anhydride. 13C NMR indicated the maleylation reaction was preferred at the C2 hydroxyl group of D-galactose, and the crosslinking reactions occurred at the C2 and C6 hydroxyl groups of D-galactose in different agar chains. Interestingly, the maleylated agar monoester had higher gel transparency (1.5%, w/v) of up to 76% than the native agar (58%). However, it showed a significant decrease in gel strength from 783 g/cm2 to 403 g/cm2, while crosslinking endowed agar with higher gel strength (845 g/cm2) and gel transparency (78.4%). The high transparency of the modified agar plate made colony observation and colony counting easy. Maleylation of agar further enhanced the freeze-thaw stability of agar gel (24.8%, 7th freeze-thaw cycles). Overall, the maleylated agar possessed superior functional properties, and it could be used as food, bacteriological, and biotechnological agar.


Asunto(s)
Galactosa , Anhídridos Maleicos , Acilación , Agar/química , Fenómenos Químicos , Anhídridos Maleicos/química
20.
Mar Drugs ; 19(9)2021 Aug 26.
Artículo en Inglés | MEDLINE | ID: mdl-34564148

RESUMEN

In this work, the physicochemical properties of maleic anhydride (MAH)-modified κ-carrageenan (κCar) (MC) were characterized and compared with those of native κ-carrageenan (NC). The Fourier transform infrared spectrum of MC exhibited that κCar was successfully modified. Thermogravimetric analysis indicated that the thermal stability of MC was decreased. When the degree of substitution was 0.032, MC exhibited a low gel strength (759 g/cm2), gelling temperature (33.3 °C), and dehydration rate (60.3%). Given the excellent film-forming ability of κCar, MC films were then prepared and were found to have better mechanical and barrier properties (UV and water) than NC films. With regard to optical properties, MC films could completely absorb UV light in the range of 200-236 nm. The water contact angle of MC films was higher than that of NC films. Moreover, the elongation at break increased from 26.9% to 163%. These physicochemical property changes imply that MC can be employed in polysaccharide-based films.


Asunto(s)
Carragenina/química , Anhídridos Maleicos/química , Temperatura , Resistencia a la Tracción , Rayos Ultravioleta , Agua/química
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